The Technology and Economic Assessment Panel (TEAP) of the United Nations Environmental Program (UNEP) has reviewed and approved a total of twelve technologies for the destruction of ozone depleting substances (ODS) [1]. For descriptive purposes, these approved technologies can be broadly classified as incineration technologies, plasma technologies including arc and radio frequency plasma, and other non-incineration technologies [1]. The most widely used current practice, both by ODS processing rate and by the number of processing units, for destruction of ODS is either by incineration or by argon plasma technology [1-2]. Both technologies use thermal oxidation as the main mechanism of destruction. ODS are fed into refractory lined reactors, which are heated to high temperatures in the order of 1200° C. Incinerators use fossil fuel-fired burners to achieve the necessary high temperatures, whereas argon plasma arc is used in the case of argon plasma technology [2-5].
As ODS are inherently fire inhibitors, extreme process conditions are needed for their destruction. Incinerators require large quantities of fossil fuels to achieve the high temperature necessary for ODS destruction. Ozone depleting substances are fed into the high temperature zone of the incinerators in relatively small quantities along with air or oxygen [2-5]. Often these incinerators do not have secondary combustion chambers and the off gases generated are simply diluted, before emitting to the atmosphere. Consequently, these incinerators require large quantities of fossil fuels to destroy small quantities of ODS, generate large quantities of flue gases containing significant amount of Cl2, F2, NOx, SOx, VOC, which are hard to remove from the flue gases [2-5]. Also, incineration processes pose a very high potential of emitting toxic products of incomplete combustion, such as dioxins and furans [6].
Plasma destruction technologies use argon, nitrogen or CO2 as the plasma forming medium to transfer energy from an electric arc into high destruction temperatures [4, 7-10]. These technologies still use thermal oxidation as their main destruction method. Direct current plasma torches are used to heat the refractory lined reactors to high destruction temperatures. ODS, air and steam are introduced into the destruction zone and the ODS are combusted. The primary destruction mechanism in these systems is still thermal oxidation and hence has similar problems such as production of Cl2, F2 and CF4, which are hard to remove from the flue gas. In these processes, the presence of excess oxygen and air in the high temperature zone still poses the potential formation of NOx, whereas operating at diminished oxygen levels lead to formation of soot, which is hard to remove. Argon plasma technology requires high flow rates of high purity argon, which makes it expensive to use.
Therefore, there is a need in the art for an improved technology for the destruction of ozone depleting substances.